From the 1850s
to the 1930s, most of Canada's oil and gas wells were drilled with a primitive
device called a cable-tool rig. The heavy, chisel-like bit was suspended on a
cable and dropped repeatedly into the rock at the bottom of the hole.
drilling was very slow, hard workand sometimes very dangerous. Progress of
just 100 metres per month was not uncommon. A modern rig can usually drill that
far in a few hours. The bits had to be pulled and sharpened frequently. Drillers
poured water into the wellbore and removed the cuttings by bailing out the
resulting "mud." If the bit encountered a reservoir, the pressure
could shoot the tool up through the rig like a bullet out of a rifle barrel.
predecessors of the types used today, were introduced in Texas in the 1890s and
in Turner Valley, Alberta, in 1925. However, they were not used widely in Canada
until exploration in Turner Valley in 1936 indicated that there were larger oil
reservoirs to be found at greater depths than earlier discoveries. After the
Second World War most cable-tool rigs were retired in favour of rotary rigs,
although a few cable-tool rigs continued to operate for many years in southern
The first well-logging instruments appeared in Canada in the 1920s. The simplest version
combined a camera, a plumb bob and a compass. This "dipmeter" was
lowered to a given depth and snapped a picture of the compass and weighted line.
The developed picture would tell drillers if the well was tilted and, if so, in
what direction. This helped avoid a common problem of wells veering off course
in the tilted and fractured underground rock formations near Turner Valley.
Another early logging instrument measured the electrical resistance in rocks
around the wellbore; a higher resistance often indicated the presence of crude
Petroleum Communication Foundation. Our Petroleum Challenge: Exploring Canada's Oil and Gas Industry, Sixth Edition. Calgary: Petroleum Communication Foundation, 1999. With permission from the Centre for Energy.